Model 238-B Antenna Matchbox

Download
Model 238-B User Manual
Model 238 B.pdf
PDF-Dokument [14.3 MB]

 

WARNING:  DO NOT USE IT'S BUILT-IN BALUN

 

The built-in Balun in the Model 238B (and Models 238 and 238A) is a 4:1 Ruthroff balun and totally worthless for this application.  DO NOT USE IT.

 

Instead, wind your own 1:1 Guanella Balun, either using RG-142 (or similar) Teflon-insulated coax, or bifilar winding.  Use FT-240-43 core(s):  1 Core for 500w, 2 Cores for 1kW, 3 Cores for 1500W.

 

See:  http://www.dj0ip.de/rf-cmc-chokes-1/different-kinds-of-chokes/d2-guanella-choke/